Module handling apparatus and method with rapid switchover capability

ABSTRACT

An apparatus and method for the rapid switchover between different height modules in an automatic module testing and handling machine. The multi-chip module (MCM) handling apparatus comprises a bottom rail and a guide rail which has an upwardly extending wall and an outwardly extending flange which form a channel. This channel provides a passageway through which a MCM of a first thickness can pass laterally such that the first MCM is in contact with the top surface which positions contact nodes provided on the first MCM at a predetermined vertical position with respect to the top surface. This handling apparatus further comprises a removable justifying plate (RJP) which is removably attached within the first channel, thereby forming a second channel. This second channel provides a passage way through which a MCM of a second thickness, which is less than the first thickness of the first MCM, can pass laterally. Thus, the second MCM is in contact with the upper surface of the RJP, thereby positioning contact nodes provided on the second MCM at substantially the same predetermined position with respect to the top surface, as the first MCM.

FIELD OF THE INVENTION

The present invention relates to an apparatus and method for the testingand handling of electronic parts, and more specifically to a multi-chipmodule handling apparatus and method with rapid switchover capability.

BACKGROUND OF THE INVENTION

The present invention relates to the testing and handling of multi-chipmodules. These modules usually consist of a printed circuit board (PCB)onto which integrated circuit chips have been applied, on one side or onboth sides, e.g. a Single In-line Memory Module (SIMM), or a DualIn-line Memory Module (DIMM). These PCB modules also consist of multiplepin edge connectors by which the PCB module is connected to anelectronic device, such as a computer motherboard, when the module isinserted into an appropriate receptacle.

The PCB module must be tested after fabrication, but prior to use, inorder to ensure high quality electronic parts. Multiple chip modulehandlers have been developed to automatically input electronic modulesinto a testing device. The machine tests the modules, and then sortsthem depending on programmed criteria. The machine can include a hopperor tray into which numerous modules to be tested are loaded. The machinethen feeds one module at a time onto a conveyance assembly which thenconveys the module to the testing device for testing via the multiplepin edge connector. After testing, the machine is programmed to directthe module onto a next station, which can be one of multiple sortingcontainers depending on the outcome of the test.

Depending on the machine model or options available, multiple chipmodule (MCM) handlers may be capable of handling both single-side anddual-sided PCB modules, as well as modules of different heights, i.e.,board thickness or chip height variations. The height difference betweendifferent types of modules can often be significant. In the past, MCMhandlers have accommodated the height difference between different typesof modules by allowing the end user to modify the configuration of theconveyance assembly prior to testing a batch of modules. This switchoverhas been accomplished by the operator removing one or more parts of theconveyance assembly and replacing them with one or more other parts thatare constructed specifically for the height of the desired module andreconfiguring all sensors, switches, and other associated components.The time involved in modifying the configuration of the MCM handler fora different height part can be significant. In particular, when changingfrom a dual-sided SIMM to a single-sided SIMM, the time requirement canbe as much as 2 to 5 minutes per switchover. Over the course of a shift,these switchovers can accumulate into a considerable amount of downtime,which is a significant loss of productivity in an automated industry.

What is needed is an automatic testing and handling conveyance assemblywhich can accommodate different height electronic modules easily andefficiently. What is also needed is an apparatus and method for therapid switchover between different height modules in an automatic moduletesting and handling conveyance assembly. What is further needed is anapparatus and method which allow for the quick and efficientreconfiguration of a conveyance assembly to accommodate eithersingle-sided or double-sided multi-chip modules.

SUMMARY OF THE INVENTION

The present invention teaches an apparatus and method for the rapidswitchover between different height modules in an automatic moduletesting and handling machine. The multi-chip module (MCM) handlingapparatus comprises a bottom rail having a top surface, and a guide railhaving a bottom surface in contact with the bottom rail top surface. Theguide rail also has an upwardly extending wall and an outwardlyextending flange which form a channel defined by the bottom rail topsurface, the extending wall and the flange. This channel provides apassageway through which an MCM of a first thickness can pass laterallysuch that the first MCM is in contact with the top surface whichpositions contact nodes provided on the first MCM at a predeterminedvertical position with respect to the top surface. This handlingapparatus further comprises a removable justifying plate (RJP) having anupper surface and a lower surface, both substantially parallel to thebottom rail top surface. This RJP is removably attached in contact withthe bottom rail top surface within the first channel, thereby forming asecond channel defined by the upper surface, the extending wall and theflange. This second channel provides a passage way through which an MCMof a second thickness, which is less than the first thickness of thefirst MCM, can pass laterally. Thus, the second MCM is in contact withthe upper surface of the RJP, thereby positioning contact nodes providedon the second MCM at substantially the same predetermined position withrespect to the top surface, as the first MCM.

The present invention provides an automatic handling and testingconveyance assembly which can accommodate different height electronicmodules easily and efficiently. It also provides a removable justifyingplate which can be quickly and efficiently attached to an MCM conveyanceassembly while the conveyance assembly is configured for a larger heightmodule, in order to accommodate a smaller height module for handling andtesting without having to disassemble the conveyance assembly. Inaddition, the present invention provides an apparatus and method whichallow for the quick and efficient reconfiguration of a conveyanceassembly to accommodate either single-sided or double-sided MCMs. Alsoprovided is a removable justifying plate which meets the aboverequirements that is rugged, durable, electrically and staticallycompatible with the modules being handled, of relatively simple designand economical manufacture, and is relatively simple to install.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an overall depiction of an automatic multi-chip module (MCM)handling and testing machine showing the major components;

FIG. 2 is a top view of one type of MCM showing the printed circuitboard, the chips and the edge connectors;

FIG. 3 is a side view of a single-sided MCM as shown in FIG. 2;

FIG. 4 is a side view of a double-sided MCM as shown in FIG. 2;

FIG. 5 is a top view of a conveyance assembly of an automatic modulehandling and testing machine, partially broken away, showing multipleMCMs being conveyed;

FIG. 6 is side sectional view of a conveyor assembly taken along line6--6 of FIG. 5;

FIG. 7 is a side sectional view of a type of testing device used inconjunction with an automatic MCM handling and testing machine showing amodule in position for testing and the contact pins used to contact themodule edge connectors;

FIG. 8 is an end view of a handling apparatus as configured fordouble-sided MCMs in both the prior art and the present invention;

FIG. 9 is an end view of a handling apparatus as configured forsingle-sided MCMs in the prior art;

FIG. 10 is an end view of a handling apparatus as configured forsingle-sided MCMs in the present invention;

FIG. 11 is a dimensional top view of the preferred embodiment of theremovable justifying plate;

FIG. 12 is a dimensional side view of the preferred embodiment of theremovable justifying plate, as shown in FIG. 11; and

FIG. 13 is a perspective view of one embodiment of a handling apparatusconfigured for single-sided MCMs where the removable justifying plate isattached by a plurality of threaded fasteners.

DETAILED DESCRIPTION

In the following detailed description of the preferred embodiments,reference is made to the accompanying drawings which form a part hereof,and in which are shown by way of illustration specific embodiments inwhich the invention may be practiced. It is to be understood that otherembodiments may be utilized and structural changes may be made withoutdeparting from the scope of the present invention.

Referring now to the drawings, FIG. 1 illustrates an automaticmulti-chip module handling and testing machine 100 which automaticallyinputs electronic modules into a testing device 300. Examples of thistype of handling machine are the Model 828-MCM & 838-DIM SIMM/DIMMModule Handlers by MC Systems, Inc., as described in the Model 828-MCM &838-DIM SIMM/DIMM Module Handlers Technical Manual, Part Number 200298,Copyright 1995, incorporated herein by reference. The machine 100 caninclude a hopper (or tray) 110 into which the numerous multi-chipmodules 400 to be tested are loaded. The machine 100 then feeds onemodule 400 at a time onto a conveyance assembly 200 which then conveysthe module to the testing device 300 for testing. After testing, themachine 100 is programmed to direct the module 400 into one of multiplesorting containers 120 depending on the outcome of the test.

A multi-chip module (MCM) 400, as shown in FIGS. 2, 3, and 4, usuallyconsists of a printed circuit board 410 onto which a plurality ofintegrated circuit chips 420 have been mounted. These chips 420 can bemounted on either one surface, known as a single-sided module 401, or onboth surfaces, known as a double-sided module 402. Included on thesemodules are contact nodes, usually in the form of edge connectors 430which have traces on both sides of the printed circuit board. These edgeconnectors 430 provide contact with an electronic device, such as acomputer motherboard, when the module is plugged in to an appropriatereceptacle connected to the device.

Various types of MCMs exist; for example, in-line memory modules. On asingle in-line memory module, or SIMM, the module has a single pitchedge connector where the traces of the edge connectors 430 are platedthrough the printed circuit board 410 so that the same information isavailable on either side of the board. On a dual in-line memory module,or DIMM, the module has a dual pitch edge connector where the edgeconnector traces are isolated and not common to each side so that theinformation is different on either side of the board. Both SIMMs andDIMMs can be single-sided or double-sided. The present invention,although primarily designed to work with SIMMs or DIMMs, willaccommodate any MCM which is designed similar to a SIMM or DIMM, as wellas many others.

FIGS. 5 and 6 depict a section of the conveyance assembly used totransport MCMs 400 from the hopper 110 to the testing device 300. TheMCM 400 is moved by a conveyor 240 along a path formed by an assembly ofrails which support the MCM 400 during conveyance. The bottom rail 220provides the base support for all types of modules. The guide rail 210restricts the upward movement of the MCM 400 as it moves along theconveyance assembly 200. The side rail 230 provides support for theconnector edge of the MCM 430 during transport.

In FIG. 7, a double-sided MCM 402 is shown in position for testing bythe testing device 300. The purpose of the testing device 300 is to makeelectrical contact with the edge connector traces 430 of the MCM. Thisis accomplished using upper and lower contactor pins 350, 360 which aremounted into upper and lower contactor assemblies 310, 320 attached toupper and lower mounting blocks 330, 340. These assemblies areprogrammed to raise and lower, as necessary, to make contact with theMCM 402 when it is in position and ready for testing. The guide rail 210provides a restraint during testing to counteract the forces applied tothe edge connectors 430 by the contact pins 350, 360. The testing device300 is programmed to send and receive the appropriate signals thatindicate the condition of the module under test. Once the test isperformed, the testing device 300 sends a control signal to a sortingmechanism which shuttles the tested modules into the appropriate sortingcontainers 120 as shown in FIG. 1.

The present invention is specifically related to the conveyance of MCMswithin the automatic MCM handling and testing machine. As previouslydescribed, the guide rail 210, shown in FIG. 8, provides both a pathwayfor and a restraint on the modules 402 being conveyed. The guide rail210 can be constructed to accommodate any size or type of MCM, whethersingle-sided, double-sided, thicker/thinner printed circuit board, orthicker/thinner chips. The bottom rail 220 provides support for any typeof MCM being handled and, when combined with the guide rail, forms amodule handling assembly.

The bottom rail 220 has a top surface 221 on which many of the MCMs,such as the double-sided MCM 402 shown, are supported by direct contact.The guide rail 210 has a bottom surface 213 which is mounted in contactwith the top surface of the bottom rail 221, an upwardly extending wall211 which is substantially perpendicular to the top surface 221, and anoutwardly extending flange 212 which overhangs the top surface 221.These two rails, the guide rail 210 and the bottom rail 220, form achannel defined by the top surface 221, the wall 211, and the flange212, through which the modules 402 pass laterally. As the modules movealong the conveyor through the defined channel of the module handlingassembly, the edge connector of the module 430 is maintained at apredetermined vertical position above the top surface 221, in order tomatch up with the testing device contactor pins 350, 360 as shown inFIG. 7.

When the automatic handling machine is set up to run a batch of modules,the module handling assembly is configured by having an appropriateguide rail 210 chosen and mounted to the bottom rail 220 to form achannel of the necessary vertical height to accommodate the modulesunder test. Both in the past, and in the present invention, if a batchof double-sided modules is being tested, the module handling assembly isconfigured as shown in FIG. 8, as described above. However, in the past,to switch over to single-side modules it was necessary to disassemblethe module handling assembly and reconfigure it as shown in FIG. 9. Thebottom rail 220 remains the same, but a new single-sided guide rail 260constructed for the single-side module 401 is used in conjunction with aspacer plate 500 such that the spacer plate is mounted with its bottomsurface 502 in contact with the top surface of the bottom rail 221. Thebottom surface of the single-sided guide rail 263 then mounts in contactwith the spacer plate top surface 501. The single-sided guide rail 260has an upwardly extending wall 261, similar to the wall 211 shown inFIG. 8, except that the vertical height of the wall 261 is shortened bythe amount equal to the thickness of the spacer 500. The single-sidedguide rail 260 also has an outwardly extending flange 262 which overhangs the top surface of the spacer 501 such that a channel if formeddefined by the top surface of the spacer 501, the wall 261 and theflange 262 through which single-sided modules 401 pass laterally. As thesingle-sided modules 401 move along the conveyor through the definedchannel of the module handling assembly, the edge connector of themodule 430 is still maintained at the same predetermined verticalposition above the top surface of the bottom rail 221, in order to matchup with the testing device contactor pins 350, 360 as shown in FIG. 7.

The thickness of the spacer 500 is based on the thickness of the lowerchip on the double-sided module 402 in FIG. 8 such that the printedcircuit board, edge connector and upper chip of the single-sided module401 are at substantially the same vertical position above the topsurface of the bottom rail 221 as the equivalent module components onthe double-sided module 402. Once the batch of single-sided modules hasbeen tested and another batch of double-sided modules is ready fortesting, the above described module handling assembly of FIG.9 must bedisassembled and reconfigured as shown in FIG. 8. This switchoverprocess must be repeated as many times a day as required to meet thetesting needs of the modules requiring testing. In addition to thecomponents of the module handling assembly, other machine componentssuch as sensors and switches must also be readjusted or realigned eachtime the disassembly and switchover process takes place. The problemwith this method of switching over from double-sided to single-sided,and back again, is the time requirement and inefficiency of thedisassembly process, as described above.

The present invention teaches an apparatus and a method for making theseswitchovers quickly and efficiently because no disassembly and noreadjustment are required. In FIG. 10, the module handling assembly ofthe present invention is configured for single-sided modules 401 suchthat the guide rail 210 for a double-sided module remains mounted incontact with the top surface of the bottom rail 221. In order to supportthe single-sided module 401 such that the edge connector of the module430 is still maintained at the same predetermined position as those ofthe double-sided modules 402, a removable justifying plate 250 ismounted in contact with the top surface of the bottom rail 221. Insteadof disassembling the module handling assembly, and replacing the guiderail 210 with the single-sided guide rail 260 and spacer plate 500, theremovable justifying plate 250 is just added to the double-sidedconfiguration.

The removable justifying plate 250 is mounted with its lower surface 252in contact with the top surface of the bottom rail 221, and its uppersurface 251 becomes part of the channel through which the single-sidedmodules 401 are passed laterally. This channel is now defined by theupper surface of the removable justifying plate 251, the wall of theguide rail 211, and the flange of the guide rail 212. Thus, thesingle-sided modules are supported by the removable justifying plate 250such that the edge connector of the module 430 is still maintained atthe same predetermined vertical position above the top surface of thebottom rail 221, in order to match up with the testing device contactorpins 350, 360 as shown in FIG. 7.

In the preferred embodiment shown in FIGS. 11 and 12, the removablejustifying plate 250 is an elongate strip of substantially rigidmaterial with the upper surface 251 relatively planar and parallel tothe lower surface 252. The preferred length 253 of the plate is 18.000inches and width 254 is 0.400 inches. The preferred method of attachmentis using two threaded fasteners 255 such that the plate 250 includes twostandard countersunk clearance holes 257 for a #6-32 screw thread,preferably located lengthwise 1.500 inches from end, 15.000 inches apartcenter-to-center, and widthwise on the centerline. FIGS. 11 and 12 showexamples of edge notching 258 and end chamfers 259. These arerepresentative of the various types of edge configurations that could bemade to accommodate plate installation into an existing machine; theyare not meant to limit the scope of the invention in anyway.

It is believed that the removable justifying plate should be fabricatedfrom an electrostatic discharge (ESD) safe material. However, anymaterial which meets the functional requirements of the presentinvention, and does not damage the multichip modules being tested, wouldbe suitable for the intended purpose of the invention.

The upper surface 251 of the removable justifying plate 250, as shown inFIGS. 10, 11, and 12, must be substantially flat once installed in themodule handling assembly. As its purpose is to provide a smooth,supportive passageway for the MCMs 401 during conveyance, the plate mustnot obstruct or hinder the movement of the modules. Therefore, it isnecessary that any attachment method chosen must adhere to thisrequirement of unobstructed conveyance.

As described above, in the preferred embodiment of the presentinvention, the removable justifying plate 250 is mounted to the topsurface 221 by two threaded fasteners 255 along the length of the plate,as shown in FIG. 13. These threaded fasteners 255 are counter-sunk intothe removable justifying plate 250 from the top and screw into a tappedhole in the bottom rail 220. Attachment of the removable justifyingplate to the module handling assembly can be achieved in many otherways, in addition to that described in the preferred embodiment. Thesemethods include, but are not limited to, use of a spring clip to attachto the guide rail flange 212, use of a spring clip to attach over theedge of the bottom rail 220, use of spring clips to attach into slots inthe top surface of the bottom rail 221, use of threaded fasteners fromthe bottom so that the removable justifying plate has holes tapped fromthe lower surface 252, and use of a hook and loop type fastener wherethe loop portion resides in a recess in the top surface of the bottomrail 251. The requisite characteristics of any attachment method arethat: 1) the locations of any fasteners must be determined based onwhether the fasteners can be removed or installed in a minimum amount oftime, without having to remove, disassemble, or reconfigure any otheraspect of the automatic module handling machine; 2) any fasteners orattachment method must be compatible with the structure and function ofthe existing machine; 3) any modifications to the existing machine toaccommodate the attachment method must be compatible with the machine'sfunction and the intended use of the present invention; and 4) thechosen attachment method must be compatible with the structure of theremovable justifying plate being used.

As shown in FIG. 12, the other critical dimension of the removablejustifying plate 250 is the thickness of the plate 256. In the preferredembodiment, this thickness is 0.130 inches. This thickness is based onthe height of the chips mounted on the bottom side of the printedcircuit board in an MCM, as shown in FIGS. 8 & 10, such that thesubstitution of the removable justifying plate for these chips, whenconveying a single-sided board, places the edge connectors 430 atsubstantially the same vertical position above the top surface of thebottom rail 221. The thickness of the plate will vary depending on thetype of multi-chip modules being tested, and the variation in heightbetween the different batches of modules for which the module handlingmachine must be reconfigured during a work shift.

Although the preferred embodiment and the figures teach of the presentinvention being used in conjunction with a change over from double-sidedMCMs to single-sided MCMs, and back again, the present invention is notintended to be limited only to these types of changes. The presentinvention is equally applicable to any situation where a larger heightmodule is being switched with a smaller height module. The controllingfactor is the difference in height between the maximum height module tobe handled and tested, and the module currently being tested. Once therange of modules to be tested has been determined for a particularshift/day, the guide rail 210, as shown in FIG. 8, is mounted to thebottom rail 220 on the automatic module handling machine. The remainingportions of the machine are then configured to handle these largestmodules. Once the machine is fully configured for the maximum heightmodules, the smaller height modules can all be accommodated by theinstallation of an appropriate removable justifying plate 250, as shownin FIG. 10, whose thickness has been determined such that the smallermodule's edge connectors remain at the same vertical position above thebottom rail as those of the maximum height module. Hence, the presentinvention is applicable to a wide range of multi-chip modules thatrequire handling and testing in an automatic module handling and testingmachine.

As can be seen from the above description, the advantages of the presentinvention include providing an automatic handling and testing conveyanceassembly which can accommodate different height electronic moduleseasily and efficiently, providing a removable justifying plate which canbe quickly and efficiently attached to an MCM conveyance assembly whilethe conveyance assembly is configured for a larger height module, inorder to accommodate a smaller height module for handling and testingwithout having to disassemble the conveyance assembly, and providing anapparatus and method which allows for the quick and efficientreconfiguration of a conveyance assembly to accommodate eithersingle-sided or double-sided MCMs. These advantages also includeproviding a removable justifying plate to meet the above requirementsthat is rugged, durable, electrically and statically compatible with themodules being handled, of relatively simple design and economicalmanufacture, and is relatively simple to install.

It is to be understood that the above description is intended to beillustrative, and not restrictive. Many other embodiments will beapparent to those of skill in the art upon reviewing the abovedescription. The scope of the invention should, therefore, be determinedwith reference to the appended claims, along with the full scope ofequivalents to which such claims are entitled.

What is claimed is:
 1. An apparatus for handling assembled multiple chipmodules (MCMs) comprising:a bottom rail having a top surface; a guiderail having a bottom surface in contact with the bottom rail topsurface, an upwardly extending wall, and an outwardly extending flangewhich forms a first channel defined by the top surface, the extendingwall and the flange, such that a first MCM of a first thickness can passlaterally through the channel, the first MCM being in contact with thetop surface to position contact nodes provided on the first MCM at apredetermined vertical position with respect to the top surface; and aremovable justifying plate having an upper surface and a lower surface,both substantially parallel to the bottom rail top surface, removablyattached in contact with the bottom rail top surface within the firstchannel, thereby forming a second channel defined by the upper surface,the extending wall and the flange, such that a second MCM of a secondthickness which is less than the first thickness of the first MCM, canpass laterally through the channel, the second MCM being in contact withthe upper surface of the removable justifying plate to position contactnodes provided on the second MCM at substantially the same predeterminedposition with respect to the top surface as the first MCM.
 2. Theapparatus as described in claim 1, wherein the first MCM is adouble-sided module which has components on both the top and bottomsurfaces of a printed circuit board, and the second MCM is asingle-sided module which has components only on the top surface of aprinted circuit board.
 3. The apparatus as described in claim 1, whereinthe contact nodes of the MCMs are single pitch edge connectors.
 4. Theapparatus as described in claim 1, wherein the contact nodes of the MCMsare dual pitch edge connectors.
 5. The apparatus as described in claim1, wherein the removable justifying plate is constructed of anelectrostatic discharge (ESD) safe material.
 6. The apparatus asdescribed in claim 1, wherein the removable justifying plate is attachedto the bottom rail top surface with threaded fasteners.
 7. A handlingand testing system for multiple chip modules (MCMs) comprising:a hopperinto which a plurality of MCMs are loaded; a testing device; and aconveyance assembly which transports MCMs from the hopper to the testingdevice and then on to a subsequent station, wherein the conveyanceassembly further comprises:a conveyor which provides movement of theMCMs, a side rail which provides support to a free edge of the MCMs, abottom rail having a top surface, a guide rail having a bottom surfacein contact with the bottom rail top surface, an upwardly extending wall,and an outwardly extending flange which forms a first channel defined bythe top surface, the extending wall and the flange, such that a firstMCM of a first thickness can pass laterally through the channel, thefirst MCM being in contact with the top surface to position contactnodes provided on the first MCM at a predetermined vertical positionwith respect to the top surface, and a removable justifying plate havingan upper surface and a lower surface, both substantially parallel to thebottom rail top surface, removably attached in contact with the bottomrail top surface within the first channel, thereby forming a secondchannel defined by the upper surface, the extending wall and the flange,such that a second MCM of a second thickness which is less than thefirst thickness of the first MCM, can pass laterally through thechannel, the second MCM being in contact with the upper surface of theremovable justifying plate to position contact nodes provided on thesecond MCM at substantially the same predetermined position with respectto the top surface as the first MCM.
 8. The handling and testing systemdescribed in claim 7, wherein the MCMs are contained in the hopper in asubstantially horizontal orientation, such that a printed circuit boardof the MCM is substantially parallel to the conveyance assembly.
 9. Thehandling and testing system described in claim 7, wherein the testingdevice further comprises a plurality of contact pins mounted on upperand lower mounting blocks such that when lowered and raised,respectively, the pins make electrical contact with contact nodesprovided on a MCM, thereby testing predetermined electrical componentson the MCM.
 10. The handling and testing system described in claim 7,wherein the subsequent station to which MCMs are conveyed after thetesting device is a sorting device further comprising multiple sortingcontainers into which MCMs are shuttled after testing based on theresults of the tests.
 11. A method for switching between a first MCM ofa first thickness and a second MCM of a second thickness, and backagain, on an apparatus for handling MCMs where each MCM is conveyedwithin a channel created by a bottom rail and a guide rail with anoverhanging guide flange such that the contact nodes on the MCM'sprinted circuit board are maintained at a predetermined verticalposition with respect to a top surface of the bottom rail, comprisingthe steps of:setting up the handling apparatus for a first MCM of afirst thickness; conveying the first MCM along the handling apparatusfor testing and handling; removably attaching a removable justifyingplate to the top surface of the bottom rail within the channel such thatthe removable justifying plate and the guide rail form a second channelthrough which a second MCM of a second thickness, which is less than thefirst thickness of the first MCM, can be conveyed with the contact nodeson the second MCM maintained at substantially the same predeterminedvertical position with respect to the top surface of the bottom rail asthat of the first MCM; and conveying a second MCM along the handlingapparatus for testing and handling.
 12. The method as described in claim11, further comprising the steps of:removing the removable justifyingplate from the handling apparatus; and conveying another first MCM alongthe handling apparatus for testing and handling.
 13. The method asdescribed in claim 11, further comprising the steps of:removing theremovable justifying plate from the handling apparatus; attaching asecond removable justifying plate to the handling apparatus in the samelocation as the first removable justifying plate such that a third MCMof a third thickness which is less than the first thickness of the firstMCM would be supported by the second removable justifying plate withcontact nodes at substantially same vertical position as the first MCMwith respect to the bottom rail top surface; and conveying a third MCMalong the handling apparatus for testing and handling.
 14. The method asdescribed in claim 13 further comprising the steps of:removing thesecond removable justifying plate from the handling apparatus; andconveying another first MCM along the handling apparatus for testing andhandling.